Question 4: The pressure in a gas cylinder containing hydrogen will leak more quickly than if it is containing oxygen. Why?

ANSWER

Hydrogen molecule is very small as compared to Oxygen molecule. Molecular mass of Hydrogen is 2 a.m.u, while that of Oxygen is 32 a.m.u. Therefore, at same temperature, the average velocity of Hydrogen molecules will be 4 times greater than Oxygen molecules (Why?         Try ½ m_hv_h²= ½ m_ov_o² ). Therefore, Hydrogen molecules will leak more quickly as compared to Oxygen molecules due to its high speed. This is in accordance with the Graham’s law of diffusion, “rate of diffusion of a gas is inversely proportional to the square root of its molecular mass”.